ROM
When you buy your Android device, it comes with what we call a “stock ROM” or the “stock firmware”. This refers to the preinstalled operating system. This ROM usually has limited functionality as defined by the phone’s manufacturer. By flashing a custom ROM, you can unlock extra features and sometimes improve the performance.
The term ROM, which stands for Read Only Memory and really has very little to do with what a custom Android ROM actually is, can be confusing. A custom Android ROM refers to a phone’s firmware, based on Google’s Android platform. Android is open source and therefore any developer can edit the code, recompile it, and re-release for a wide variety of devices. Users can install ROMs to change a device’s appearance and behavior. ROMs are developed by the Android community, often times by a group of core developers who do this purely out of passion for modding. This means that most are completely free. Custom ROMs are available for phones, tablets, media players, smart watches and almost any type of device running Android.
Flashing a ROM is easy and if you follow instructions, you barely need to know what you’re doing. You should know that if you do something incorrectly while flashing a ROM, you risk rendering your phone inoperable. This is rare but can happen if you aren’t careful, and it’s called “bricking”.